For a good general description of Permaculture, check out Permaculture on Wikipedia. You'll love it and get lost!
Remember to come back to Seattle Permaculture for local info.

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I often describe Permaculture as a way to implement designs in the land (or in our own lives) that most
efficiently *and lovingly* integrate Natural Ecosystems with Human Needs. Not just organic farming,
but loops of systems that benefit each other.
Examples: greywater from the kitchen sink watering herbs and flowers that are used for meals in the kitchen.
electricity generated from an ecosystem's abundance (sun, wind, water) for the use of humans that in turn protect
that ecosystem from damage combining plants and animals in such a way that they can nurture each other.

Permaculture-thinking is important because it's a tool by which humans can have fulfilling lives and use
less resources. (inserted by kelda)

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How about this one from Randy Hayes:
A collection of diverse and rewarding lifestyles that many would want to emulate, and if they all did,
the planet's natural systems and wildlife populations would flourish, increasingly, each generation.